The cable news channel Al Jazeera America, which debuted in 2013 to great fanfare when it promised to cover American news soberly and seriously, will be shutting down by the end of April. The move was announced at a companywide meeting on Wednesday.

In a memo to the staff, Al Jazeera America’s chief executive, Al Anstey, said the “decision by Al Jazeera America’s board is driven by the fact that our business model is simply not sustainable in light of the economic challenges in the U.S. media marketplace.”

“I know the closure of AJAM will be a massive disappointment for everyone here who has worked tirelessly for our long-term future,” he continued, using the company acronym. “The decision that has been made is in no way because AJAM has done anything but a great job. Our commitment to great journalism is unrivaled.”

At the companywide meeting, Al Jazeera America staff members, some in tears, were told that the decision to shutter the network had not been unanimous. Some of the channel’s leadership argued that the network provided an important service, and continued to win awards for its coverage. But in the end, the decision was an economic one. The channel, it was felt, had fallen victim to the lack of a business model beyond continuous support from Qatar, the energy-rich country that owns Al Jazeera.

Some staffers saw that as a tacit admission that falling oil prices were behind the closure, though a spokeswoman for the company denied that on Wednesday.

Beyond its oil wealth, Qatar is one of the world’s top exporters of liquefied natural gas, whose price has also tumbled.

Mr. Anstey said that once the cable news network shuts down by April 30, Al Jazeera would expand its digital presence in the United States. The expansion “would bring new global content into America.”

Al Jazeera America went on the air in August 2013 after Al Jazeera bought Al Gore’s Current TV for $500 million. It promised to be thoughtful and smart, free of the shouting arguments that have defined cable news in the United States over the last decade. But meaningful viewership never came, with prime-time ratings sometimes struggling to exceed 30,000 viewers.

To make matters worse, turmoil hit the newsroom last year when staff members complained bitterly of a culture of fear. There was an exodus of top executives, along with a pair of lawsuits from former employees that included complaints about sexism and anti-Semitism at the news channel.

In May, Ehab Al Shihabi, the chief executive of Al Jazeera America, was replaced by Mr. Anstey. Morale improved, but ratings remained low.

The closure, which will cost hundreds of employees their jobs, highlights the difficulties of establishing a robust cable news presence in an increasingly crowded media marketplace, and one that faces ever more competition from the web — the ultimate 24-hour news medium.

Current TV, before being bought by Al Jazeera, had struggled for years to find an audience, and to define its place in the news landscape. Fusion, a cable news network and digital publication aimed at younger audiences, lost the backing of one of its corporate parent companies, Disney, in recent weeks, following reports that it, too, had struggled to find its footing with audiences. Even established players like MSNBC have been forced to revamp in recent years.

Andrew Heyward, a former president of CBS News who is now an adviser to media companies, said in an interview that Al Jazeera America had faced an uphill battle from the beginning.

Cable news “is a very well-served market, not to say saturated, and you have three powerful, well-established players,” he said, referring to Fox News, MSNBC and CNN. “Endemically, it’s not quite clear that the world was waiting for a new 24-hour cable channel in the U.S., and cable operators certainly weren’t waiting for it,” he said, describing the limited distribution the channel received.

“They came kind of swaggering into the arena, saying we’re going to do higher-end stories and represent people who are under-represented,” Mr. Heyward said, a proposition that played better on paper than in practice. And the network brought something of a British sensibility and judgment, he said, which did not translate as well to cable news as it might in other arenas.

“This is not ‘Downton Abbey,’ ” he said.

All these problems were exacerbated, he said, by the fact that a brand associated with the Arab world was a tougher sell in the United States than it was in Europe.

And Al Jazeera America has not been free of controversy in recent months. In November, the news station’s general counsel, David W. Harleston, was suspended following a report in The New York Times that he did not appear to be licensed to practice law. Among the varied legal work Mr. Harleston had done for Al Jazeera America was his involvement in wrongful termination lawsuits brought by former employees. Legal experts have cautioned that Mr. Harleston’s lack of a law license could potentially leave the network vulnerable in those lawsuits, primarily over issues of confidentiality.

On Dec. 27, Al Jazeera America aired an hourlong documentary that linked some of the biggest stars in Major League Baseball and the National Football League to performance-enhancing drugs. The most prominent athlete mentioned was the Denver Broncos quarterback Peyton Manning, who angrily denied the report, calling it “complete garbage” and “totally made up.” The baseball players Ryan Howard and Ryan Zimmerman have filed defamation suits against the network.

When told Wednesday of Al Jazeera America’s plans to shut down, Mr. Manning deadpanned, “I’m sure it’s going to be just devastating to all their viewers.”